Generally, a track on which a train or the like travels and in which a track bed is provided on a roadbed and then a sleeper and a rail are provided on the track bed is widely known. Here, the track bed is a track material that serves to highly disperse a train load transmitted from the rail and the sleeper to deliver it to a roadbed and to fix the sleeper at a predetermined position, and gravel (or crushed stone) or concrete is used for the track bed. Conventionally, a track bed gravel (or a gravel track bed) track is referred to as a ballast track.
A structure of such a track is generally provided so that sleepers are arranged on a track bed formed on a roadbed and then a pair of rails is provided in parallel at regular intervals to be attached to the sleepers. A track bed configuring such a track includes ballast, a slab or the like, that is selected in consideration of various conditions of a train route. Specifically, a ballast track, which uses ballast including gravel, crushed stone, and the like, is widely known. Because the track bed using such ballast is superior from an economical aspect while reasonably supporting a running of a heavy train due to a characteristic of the track bed, it has been employed for a very long time. Such ballast including gravel, crushed stone, and the like has functions for securely maintaining sleepers, uniformly distributing a load that is delivered from a train via the rail and the sleepers to the roadbed, allowing the track to have elasticity, facilitating damping work and the like, enhancing drainage of the track to prevent generation of mud or weeds, and so on.
FIG. 1 is a cross-sectional view of a bed gravel track, and FIG. 2 is a view for describing a damaged form of track bed gravel of the bed gravel track.
As shown in FIG. 1, a bed gravel track 10 is formed on a reinforced roadbed 11, and a weight loaded from wheels of a train is delivered to track bed gravel 12 through a rail 14 and a sleeper 13, and thus the weight is dispersed at such track bed gravel 12 through a contact point of each particle of a track bed.
At this point, a function of the track bed gravel 12 is to uniformly distribute pressure of a lower surface of the sleeper 13 to the reinforced roadbed 11, and the track bed gravel 12 secures a track bed resistance force in a longitudinal direction of the sleeper 13 and elastically supports such a sleeper 13 to buffer an impact force, thereby reducing damage to the track. Also, such track bed gravel 12 is able to fix the sleeper 13 at a predetermined position, correct a track irregularity, and allow renewal work of a sleeper to be facilitated.
In particular, crushed gravel is mainly used as a material of the track bed gravel forming the track bed gravel 12, and the crushed gravel is provided by, for example, crushing slickensides with a crusher to have a grain size distribution in which grain sizes in a range of 10 to 65 mm are properly mixed. At this point, a thickness of the track bed gravel may be determined by a shape dimension of the sleeper 13, a distance between sleepers 13, an ability of a track bed material to disperse a load, a magnitude of a train load, and a supporting force of a roadbed.
Also, such track bed gravel is damaged by a dynamic load of the train, and, for example, consolidation, a lateral flow, a roadbed penetration, granulation, and the like may occur as such damage of the track bed gravel shown in FIG. 2. Among the damage, consolidation and a lateral flow occur by vibration generated due to a running of a train and are the cause of a track irregularity of the track bed gravel such that there is a problem in that maintenance is frequently required due to such damage.
In addition, a variety of causes may result in such damage to the bed gravel track, and prominent causes among the variety of causes may be vibration generation due to a dynamic load, a settlement and a lateral flow of the track bed gravel due to such vibration generation, and a weakness effect of the roadbed due to rainwater.
Such track bed gravel should be preserved and managed so as to consistently maintain a cross-sectional shape at a time when it was constructed, and thus there is a problem in that permanent management is required to maintain a cross section of the track bed and secure a resistance force by consistently performing track bed trimming, gravel supplementing, and the like since track bed relaxation and gravel scattering due to vibration when a train runs, a collapse of a cross-sectional area of a track bed shoulder due to a maintenance person entering the track, a loss by gravel flowing into a collecting well, a drainage canal, or the like of a trackside, and so on.
Meanwhile, FIGS. 3a and 3b are diagrams respectively illustrating a mechanism in which a loose sleeper occurs at a track.
As shown in FIG. 3a, a ballast track has a structure in which ballast 12 is formed on the reinforced roadbed 11 and the concrete sleeper 13 is disposed between the ballast 12 and the rail 14, and the concrete sleeper 13 and the rail 14 are fastened to each other by a rail fastener 15.
At this point, when a train 21 repeatedly passes, the concrete sleeper 13 is upwardly and downwardly moved due to a normal load of the train 21 as shown in FIG. 3b, and the ballast 12 such as gravel and the like is settled when a time has elapsed such that a space underneath the concrete sleeper 13 is expanded as indicated by a reference numeral A.
As a result, a floating phenomenon of a sleeper, in which a space is formed underneath the concrete sleeper 13, occurs when the time has elapsed. The sleeper that has undergone such a floating phenomenon is referred to as a loose sleeper, and the concrete sleeper 13 is upwardly and downwardly moved whenever the train 21 passes over the loose sleeper, which degrades ride quality as the concrete sleeper 13 is gradually and severely moved, and thus great impact is delivered to the concrete sleeper 13 and the like when the train 21 is passing and problems, in which an amount of maintenance and a cost thereof are increased, are caused.
In other words, when no load exists at a ballast track, the concrete sleeper 13 which is in a state of not being in contact with the ballast 12, for example, gravel or crushed stone, and hanging on the rail 14 is referred to as a loose sleeper. When such a loose sleeper occurs, the ballast 12 and the loose sleeper collide with each other when the train travels such that a track condition is rapidly degraded by a crushing of the ballast 12 and generation of mud. Furthermore, in a section at which a plurality of loose sleepers occur, upward and downward displacements are generated at the rail 14 which is installed and supported by the concrete sleeper 13 and thus a track irregularity develops and a problem, in which damage to the track is increased, occurs.
Specifically, a differential settlement of the track is generated by a difference between a degree of compaction of the track bed gravel underneath the concrete sleeper 13 and stiffness of an upper roadbed including the reinforced roadbed, such that problems are generated such as the ride quality degradation, stability degradation of a train service, an increase of a maintenance cost, and so on.
Also, when the train does not run, generation of the differential settlement causes the occurrence of a loose sleeper from which a sleeper hangs on a rail by means of a stiffness of a track panel, and the occurrence of the loose sleeper is very difficult to visually determine so that there is a problem in that proper maintenance may not be performed.
Meanwhile, FIG. 4 is a diagram illustrating maintaining ballast of a sleeper at a track connector by filling a filler according to the related art, and FIG. 5 is a diagram illustrating maintaining ballast of a sleeper at a track connector using oil pressure according to the related art.
As a settlement compensation apparatus according to the related art, a sand bag, a stabilization liquid sprayer, and a method of filling a fusible bag with gravel and the like to install the fusible bag underneath a track have been disclosed. For example, in order to maintain a settled state when ballast is settled, a solid (gravel and the like) filler 32 is filled inside a housing 31 of a predetermined shape installed in ballast underneath a track to stabilize the ballast as shown in FIG. 4 or oil pressure 41 provided through an oil pressure valve 42 is used as shown in FIG. 5.
In an automatic settlement compensation apparatus according to the related art, the settlement compensation apparatus using oil pressure shown in FIG. 5 cannot easily respond to a differential settlement that is generated at left and right sides of a sleeper, and cannot automatically compensate for the differential settlement so that there is a problem in that maintenance is not easy.
Meanwhile, as the related art for addressing the above described problems, an invention filed as a patent application by the present applicant of the present disclosure is disclosed in Korean Patent Publication No. 2013-0137465, entitled of “Automatic Settlement Compensation Apparatus for Rail Tie of Track Connector and Construction Method Thereof,” and, when a track settlement is generated at a track connector between a directly fastened track and a ballast track, the invention automatically compensates for a ballast settlement by means of a mechanical engagement of upper and lower parts of a housing and an expansion force of an air bag when the ballast settlement is generated, and also can easily respond to a differential settlement, which is generated at left and right sides of a sleeper, by disposing an automatic sleeper settlement compensation apparatus at each of the left and right sides of the sleeper to compensate for the differential settlement by means of these apparatuses which operate independently. At this point, in such an automatic sleeper settlement compensation apparatus of a track connector, an inner container and an outer container of the apparatus are fastened to the sleeper.